Adjustable inductor



United States Patent 3,358,255 ADJUSTABLE INDUCTOR Joseph C. Digilio, Burlington, Mass., assignor to Cambridge Thermionic Corporation, corporation of Massachusetts Filed June 8, 1965, Ser. No. 462,317 8 Claims. (Cl. 336-83) The field of this invention relates to shielded adjustable inductor devices which are particularly suited for miniatun'zation.

Objects of the invention are to provide inductor devices of the above type, especially coil forms, which have particularly good electrical properties and can be finely and accurately adjusted; to provide such devices which have a low profile and a relatively large winding area; and to provide such a device that can be simply and comparatively inexpensively manufactured with high precisionand ruggedness, and for permanently uniform performance.

The substance of the invention can be briefly summarized as follows.

The coil of the inductor is wound on the form portion of a unitary supporting body which also has an adjustment portion capable of receiving a tuning core for complete withdrawal from the coil. The construction is such that the gap between form portion and tuning core can be made very small and that all diameters which contribute to precise and permanently stable performance can be made concentric and with high precision. The supporting body has, approximately intermediate of coil form and adjustment portion, flange means wherein contact pins are fastened and which carries on its periphery a cup core surrounding the form with the exception of an opening that makes the tuning core accessible for adjustment. A cup core cap is arranged at the pin side of the flange means and serves as a spacer between outwardly ex tending bosses for the pins. The flange is square to prevent relative rotation of the parts which completely fill a housing of smooth and low profile beyond the pins. The housing reaches nearly to the end of the cup core and has a cover which upon being fastened to the housing, holds the entire assembly securely together without any other fastening instrumentalities.

These and other objects and inventive aspects will ap pear from the following description of two practical embodiments of the invention, by way of example.

The description refers to a drawing wherein FIG. 1 is the plan view of an inductor according to the invention;

FIG. 2 is a section on line 2-2 of FIG. 1;

FIG. 3 is a bottom view detail of the cup core;

FIG. 4 is a plan view of the cup core cap; and

FIG. 5 is an axial section in part, similar to FIG. .2, of another embodiment of the invention.

The device according to the invention is built up on a supporting and coil form body which is molded of electrically and mechanically high quality insulating material, such as glass fiber filled diallyl phthalate resin. This body has a square header flange 12, a cylindrical coil form proper 14, and an adjustment sleeve 16.

The header flange 12 has bosses 12.1, one at each corner, and with chamfered projections 12.2 which serve to insulate the pins from the housing and the lower cup core plate and to keep the device above the mounting board, preventing the formation of moisture traps. Molded into the header bosses are four terminal pins 18 with inner terminal turrets 18.1 for connection to the winding which is schematically indicated at 20 and can have any desirable construction within the available space. The terminal Cambridge, Mass., at 5 3,358,255 Patented Dec. 12, 1967 pins may be spaced to fit a printed circuit grid spacing, but can be made for use in any appropriate socket, depending on the use of the device. The inner terminals are contained in recesses 18.3 of the head flange corners. The header flange has an interior ledge 12.5 for limiting the movement of the tuning core.

The coil form proper 14 has a smooth bore to provide a close fit with a smooth tuning core. The exterior is round to fit the opening of a cup core.

The adjustment sleeve 16 is threaded at 16.1 preferably with a shallow trapezoid thread suited for exact dimensioning in cooperation with the tuning core thread. As will be discussed more in detail hereinafter, the adjustment sleeve has suflicient length to accommodate the entire tuning core for complete withdrawal thereof.

The magnetic circuit consists of the cup core 21, the cup core cap 22, and the tuning core 25. The cup core 21 has a generally square shape as shown in FIG. 3, with a ledge 21.1 for contacting the cup core 21, a round top opening 21.2 for access to the tuning core, and four corner recesses 21.5 to provide space for the terminal pin turrets 18.1 and coil ends. The cup core cap 22 to square to fit the cup core 21, has, as shown in FIG. 4, cut out corners 22.1 for the pin bosses 12.2 of the body 10, and a central opening 22.2 for the adjustment sleeve 16 of the body. It will be noted that the cup core 21 reaches with its rim over the flange 12 towards the cup core cap 22, completing the magnetic circuit. The tuning core 25 has a threaded section 25.1 fitting the thread of the adjustment sleeve 16 and integral therewith a smooth tuning section 25.2 which fits the coil form 14 exactly with a minimal gap. The thread section extends beyond the tuning section for stopping engagement with the shoulder 12.5. The magnetic components are made of powdered iron or ferrite. The tuning core 25 has a notch 25.5 accessible through opening 21.2, for an adjusting tool.

The metal housing 30 has a square top portion 30.1 for the cup core and a round bottom 30.2 completely enclosing the adjusting components except for four holes for the pin projections 12.2 as above described. This round embossment is intended to reach into a mounting board or socket. It will be evident that this mounting and circuit connecting construction can be appropriately modified to suit the environment at hand. The cup core 21 reaches somewhat above the housing 30 so that by closely fitting the metallic cover 31 to the housing and the contents thereof, the entire assembly is firmly secured. The cover rim can have slits 31.1, rendering it resilient. Furthermore, the cover can be positively secured to the housing after assembly such as by soldering as indicated at 32.

The modification shown in FIG. 5 differs from the above described construction by the formation of the main body and by the adjustment thread. The main body, instead of being unitary as in FIG. 2, is here divided into a liner and a head 112 which latter is molded onto the liner. This permits the liner to be made from a material especially suited for the different adjustment thread, such as for example polypropylene. The liner has here a flange 110.1 that fits a oounterbore of the cup core 121. Adjustment is provided by means of internal resilient lands 16.5 with self-threading engagement of the thread 125.1 of the tuning core. This construction provides a locking torque. The other components of the modification according to FIG. 5 are essentially the same as of FIGS. 1 to 4, and it will be understood that the doubly molded body construction can he used with the fully threaded adjustment of FIG. 2, and that self-threading lands can be used with a body of unitary material as in FIG. 2.

It will now be evident that the above described inductor has a variety of advantages, including the following ones.

Coil forms according to the invention permit the use of a very small gap between the tuning core and the coil form, and a coil form with minimal dielectric mass which is advantageous because the critical constants vary with temperature so that a minimal dielectric mass is favorable.

The coil form and the tuning core can be easily fabricated to close tolerances which provides a favorably narrow and uniform: gap. This is made possible by the sep aration of the core tuning section from the threaded section which is always wholly removed from the impedance elements and cannot introduce disturbing effects.

In spite of the possibility of complete withdrawal of the core, the device is of minimal length. The thread length is minimal, and the core tfit can be made optimal because precision finish and centering is possible throughout manufacture, so that the gap is uniformly constant and of minimal width also for that reason.

I claim:

1. An inductor device comprising:

an elongate support formed as a unitary insulating body having a hole through its entire length with a coil form portion at one end, with an internally threaded adjustment sleeve portion at the other end, and with flange means intermediate the coil form portion and the adjustment sleeve portion;

tuning core means within said insulating body having at one end a tuning portion slidable within said ooil form portion and at the other end a threaded core adjustmentportion engaging the thread of said ad justrnent sleeve portion for withdrawal of the tuning. portion from the coil form portion;

cup core means surrounding said coil form portion; andsaid flange means; and

terminal means extending from said flange along and surrounding said adjustment sleeve portion. 2. Device according to claim 1 wherein said flange means has bosses and corresponding inner recesses arranged outside of said adjustment sleeve portion, and which further comprises contact pins molded into said means, and

a cup core cap at the adjustment sleeve portion side of said flange means and extending to said rim of the cup core. 5. Device according to claim 4 wherein said flange means and said cup core and cup core cap are square to prevent relative rotation between the insulating body and the cup coreand the cup core cap.

6. Device according to claim 4 further comprising ahousing having a bottom portion of reduced diameter within said terminal means for said adjustment sleeve portion, and an open top portion for said cup core and attached to the housing a cover for confining and holding together the insulating body and the cup core and the cup core cap.

7. Device according to claim 6 wherein said cover and; said cup core have central perforations for access to said tuning core means.

8. Device according to claim 1 wherein said flange means is of different material than said insulating body and molded around the body.

References Cited UNITED STATES PATENTS 2,430,990 11/1947 Moore 336-87 LEWIS H. MYERS, Primary Examiner. T. J; KOZ M-A, AssistantExaminer. 

1. AN INDUCTOR DEVICE COMPRISING: AN ELONGATE SUPPORT FORMED AS A UNITARY INSULATING BODY HAVING A HOLE THROUGH ITS ENTIRE LENGTH WITH A COIL FORM PORTION AT ONE END, WITH AN INTERNALLY THREADED ADJUSTMENT SLEEVE PORTION AT THE OTHER END, AND WITH FLANGE MEANS INTERMEDIATE THE COIL FORM PORTION AND THE ADJUSTMENT SLEEVE PORTION; TUNING CORE MEANS WITHIN SAID INSULATING BODY HAVING AT ONE END A TUNING PORTION SLIDABLE WITHIN SAID COIL FORM PORTION AND AT THE OTHER END A THREADED CORE ADJUSTMENT PORTION ENGAGING THE THREAD OF SAID ADJUSTMENT SLEEVE PORTION FOR WITHDRAWAL OF THE TUNING PORTION FROM THE COIL FORM PORTION; 